Bonded non-woven fabric

ABSTRACT

D R A W I N G IMPROVEMENT IN THE COAGULATION OF BINDER IMPREGNATED NONWOVEN FABRICS BY PASSING THE NONWOVEN FABRIC IMPREGNATED WITH A COAGULATABLE BINDER INTO OPERATIVE CONTACT WITH AN OPEN FLAME WHEREBY TO RAPIDLY COAGULATE AT LEAST A SUBSTANTIAL PORTION OF THE BINDER.

July 6, 1971 P. PETERSIK ETAL BONDED NONWOVEN FABRIC Filed Sept. 9, 1968 FIG. 2

mvmmze. PHER PUERSIK v ADJLF GRABER United States Patent Ctfice 3,591,407 BONDED NON-WOVEN FABRIC Peter Petersik, Lutzelsachsen, Bergstrasse, and Adolf Graber, Weinheim an der Bergstrasse, Germany, assignors to Carl Freudenberg, Patentabteilung, Weinheim an der Bergstrasse, Germany Filed Sept. 9, 1968, Ser. No. 758,387 Claims priority, application Germany, Sept. 26, 1967, P 16 19 054.8 Int. Cl. B44d N44 US. Cl. 117-46 Claims ABSTRACT OF THE DISCLOSURE Improvement in the coagulation of binder impregnated nonwoven fabrics by passing the nonwoven fabric impregnated with a coagulatable binder into operative contact with an open flame whereby to rapidly coagulate at least a substantial portion of the binder.

This invention relates to nonwoven fabrics. It more particularly refers to such fabrics having coagulated binders.

Nonwoven fabrics are well known. It is also known to be desirable to provide binders in such nonwoven fabrics whereby to render such fabrics substantially dimensionally stable. It has been considered desirable to utilize a rubber (natural or synthetic) or a synthetic resin as the binder. Such binder has been introduced into the nonwoven fabric by impregnation thereof in the form of a solution, suspension, dispersion or emulsion. It is also known to utilize and impregnate the binder into the fabric in foam form. The most common impregnant used today is the latex.

In the past, a problem has existed in that after impregnation of the fluid form binder, the liquid carrier medium had to be removed and the deposited binder vulcanized. Usually the liquid carrier was removed by heating and evaporation, usually in a drying chamber.

Evaporation of the liquid medium will usually tend to cause the binder to migrate towards the surfaces of the fabric, with the result that there may be too little binder in the centre of the fabric, with the risk that the fabric may delaminate.

It is known that binder migration can be reduced if the binder is caused to coagulate out in the fleece from the liquid medium, before evaporating that medium. The impregnation medium is generally chosen so as to be heat coagulatable, that is to say coagulation occurs on heating the medium to, for example, 60 C. However, even such a coagulation process permits some migration, at least during the initial heating thereof up to coagulation temperature. This heating is therefore conducted as rapidly as possible, generally by infrared heaters. Even with infrared, however, heating is not as rapid as desirable and some migration almost inevitably does occur,

Another problem exists in that the nonwoven fabric cannot conveniently be supported while it is being subjected to infrared radiation heating and so it tends to sag or stretch under its own weight. Distortion of the fleece thus often occurs.

It is therefore an object of this invention to provide a novel method of applying binder to a nonwoven fabric.

It is another object of this invention to provide a novel means of coagulating an impregnated binder.

Other and additional objects of this invention will become apparent from a consideration of this entire specification including the drawing and claims hereof.

In accord with and fulfilling these objects, one aspect of this invention resides in the use of an open, hot flame 3,591 ,407 Patented July 6, 1971 in direct contact with a nonwoven fabric in order to coagulate at least a substantial portion of a coagulatable binder impregnated therein.

Understanding of this invention will be facilitated by reference to the accompanying drawing in which:

FIG. 1 is an elevation schematic view of one embodiment of this invention; and

FIG. 2 is similar to FIG. 1 showing an alternate embodiment.

According to the invention coagulation of the binder is achieved by heating the fleece through contact thereof with at least one hot flame to a temperature such that coagulation of the binder occurs but that sorching of the fabric does not occur. The term hot flame refers to any flame that results from normal burners, such as gas burners of the conventional type, and which has a flame temperature of several hundred degrees centigrade, or higher. The specific temperature of the flame is not critical but it is preferably at least about C.

Contact of the impregnated fabric with flame must naturally be conducted under conditions such that scorching of the fabric does not occur. Appropriate conditions can readily be selected by anyone skilled in the art. The large amount of liquid impregnation medium, generally water, that is present in the fabric will tend to prevent scorching of the fabric provided] that the contact with the flame is not continued for so long or to such a high temperature as to result in any substantial drying of the fabric. Preferable flame temperatures are about 1100 C. whereby providing a temperature in the impregnant medium of up to about to C. It has generally been found that a water saturated fabric can be contacted with such flames for about 0.1 to 10 seconds without there being any risk of scorching. It is not essential that all the binder should be coagulated during the flame contact, provided that at least a substantial proportion of the binder, suflicient to impart dimensional stability to the fabric, is coagulated, However, in practice it is preferred that substantially all the binder is coaguated by the flame contact for reasons more fully set forth below.

Referring now to the drawing and particularly to FIG. 1 thereof, there is shown a fleece 1 being impregnated with a suitable binder by passing between a pair of rollers 2 and 3 one of which serves to apply impregnant 4 to the fabric. The impregnated fabric 5 then passes in contact with a series of flames 6 and thence onto a transfer plate 7 and into a drying and vulcanizing oven 8. FIG. 2 is very similar to FIG. 1 but shows a vertical pass through the flames.

Contact with the flame is achieved simply by passing the fabric, generally immediately after impregnation, through one or more flames. If desired the flames may act on both sides of the fleece simultaneously or sequentially. The fabric may be moving in any desired direction at the time of contact. For example it may be moving vertically, horizontally or at some angle therebetween. The fabric may, and generally is, unsupported while it is being contacted with the flame. The disadvantages that occurred previously when the unsupported fabric was subjected to infrared radiation are substantially avoided or at least minimized in the process of the invention for two reasons. Firstly, the rapid coagulation rapidly gives increased strength to the fabric so that there is less risk of sagging. Secondly, the rapid coagulation allows the distance over which the fabric has to pass unsupported to be very much less than was necessary when infra red radiation was used.

Practice of this invention is particularly advantageous when substantially all the impregnated binder is coagulated by contact with the flame. It is then possible to squeeze the liquid impregnation medium remaining in the fabric thereout of before passing the fabric into the drying chamber in which final drying of the fabric, and generally also vulcanization, is conducted, By squeezing, for example between two squeeze rolls, a large proportion of the liquid medium, for example 75%, can easily be removed and so only the small remainder, 25%, has to be removed by evaporation. As a result the drying chamber consumes much less energy for the final drying than is required when all the liquid medium has to be evaporated out. There are two reasons why this preliminary squeezing could not be conducted satisfactorily in prior processes. Firstly, the binder generally had not been coagulated sufliciently to give sufficient stability to the fabric to prevent distortion during the squeezing. Secondly, the liquid medium still contained dissolved or suspended therein a considerable amount of binder, and this would have been squeezed out at the same time as the liquid medium.

The following is an example of the invention.

A fiber fleece consisting of:

Percent Rayon fibres 20 Nylon fibres 70 Wool is prepared by carding. The fleece has a weight of 5.5 ounces per square yard and a specific gravity of 0.0035. This fleece is then needled whereby the loom operates at 200 perforation cycles per minute. The beam is set at 2 inches and the stroke is 2- /2 inches. After the first pass through the loom, the fleece is removed from the carrier, turned over and needled again. After needling, the fleece is impregnated with a heat sensitized polyacrylate latex, which has a normal coagulation temperature of 80 C.

The fleece is impregnated wtih this coagulatable latex at room temperature. The latex is dispersed in an aqueous medium. Its solids content is 48%. After impregnation the fleece is squeezed until it has a wet pick up to 400%. After impregnation it is run between two carrier belts. There is a gap of 6 cm. between these two belts. Here, the fleece hangs down a little bit. Under this gap are arranged in line of 6 Bunsen burners. This flame of the Bunsen burner touches the Wet fleece. The fleece passes over this heating zone with a speed of about 10 m./min. Thereby the impregnant is coagulated immediately upon the fleece being touched by the hot flame. Subsequently the fleece passes through a coventional dryer at a temperature of 120 C. in order to drive ofi the surplus water.

The fabric fibers may be continuous or staple and may be of substantially any composition conventionally used to make non-woven fabrics. These include nylon, cellulosics, wool, polyester, acrylics, etc.

The binders are conventionally heat coagulatable materials such as natural and synthetic rubber, polyacrylates,

etc. a

What is claimed is: l

1. In the process of producing a bonded, nonwoven fabric by impregnating a nonwoven fabric with a coagulatable fluid-form binder, coagulating said binder, removing the fluid binder carrier, and vulcanizing the binder; the improvement which comprises coagulating at least a substantial portion of the binder by passing the impregnated fabric into contact with an open, hot flame for a time sufiicient to coagulate said binder but insufficient to scorch said fabric.

2. The improved process claimed in claim 1 wherein said binder is heated to a temperature of about to C.

3. The improved process claimed in claim 1 wherein said impregnated fabric and said flame are in contact for about 0.1 to 10 seconds.

4. The improved process claimed in claim 1 wherein substantially all of said binder is coagulated by said flame and wherein said impregnant fluid is to a substantial extent removed after said coagulation by squeezing.

5. The improved process claimed in claim 1 wherein said binder is a polyacrylate.

References Cited UNITED STATES PATENTS 3,136,832 6/1964 Ballmer 264255 3,281,258 10/1966 Callahan 117-163X 3,312,584 4/1967 Charlton et a1. 117163X ALFRED L. LEAVITT, Primary Examiner E. G. WI-IITBY, Assistant Examiner US. Cl. X.R. 

